Exemplary embodiments of the present invention relate to a multilayer wiring board and, more particularly, to connecting parts which electrically connect circuit boards together and a multilayer wiring board which is laminated using the connecting parts.
Reference numeral 106 in FIG. 7 denotes a multilayer wiring board of conventional art. This multilayer wiring board 106 is composed of a plurality of single layer circuit boards 159 laminated with adhesive layers 149.
In each circuit board 159, wiring film 153 is arranged on a base substrate 152, and electronic parts 154 are mounted on the wiring film 153. The circuit boards 159 are connected by connecting parts 101. Here, the connecting part 101 is composed of a through the hole formed in the adhesive layer 149 and conductive material filled within the through-hole. The wiring films 153 of the adjacent circuit boards 159 are electrically connected each other by the connecting parts 101.
The connecting part 101 having the structure described above is called an “inner via.” Other than this, the multilayer wiring board can be laminated by use of an as disclosed in JPA S61-206107 and JPA 2004-139880.
The inner via described above, however, requires processes for forming through-holes and for filling conductive material, thereby causing high cost and low reliability.
On the other hand, while a fabrication process becomes simple by using the electrode sheet, yield of the multilayer wiring board is low because of variations in electrode sheet thickness. Further, there is also a demand that connecting parts be mounted by using the same mounter as that for electronic parts.